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RE: Flight capablities of Archie & Confucius? Not so good...

Eike's reconstruction of Archie behaviour reminds me strongly of some agamid
lizards (e.g. Lophognathus), which perch anything from centimeters to metres
above the ground and throw themselves at passing prey items, hitting the
ground running (sometimes bouncing first). It doesn't need great flight
capability to make a living at it.

Dr John D. Scanlon, FCD
Riversleigh Fossil Centre, Outback at Isa
"Get this $%#@* python off me!", said Tom laocoönically.

-----Original Message-----
From: evelyn sobielski [mailto:koreke77@yahoo.de] 
Sent: 18 May, 2010 4:40 PM
To: dinosaur@usc.edu
Subject: Re: Flight capablities of Archie & Confucius? Not so good...

> > It is perhaps significant that kakapos are
> effectively
> > flightless, but still use their wings to parachute to
> safety
> > from trees etc without getting hurt. For all that can
> be
> > said, Archie had a better wing loading than a kakapo.
> Kakapos, though, are superb climbers.
> But I take your point.  I suspect that the wings of
> _Archaeopteryx_ and small non-avialan maniraptorans (e.g.,
> microraptorines, _Rahonavis_, _Jinfengopteryx_) were
> employed to help get them out of trees.

No, not trees. What I mean is that the ability to parachute/glide safely
down from *any* significant elevation that can be reached is apparently so
advantageous that it is lost last in neoflightless lineages. Kakapos use
trees, because they climb very well. _Threskiornis solitarius_ used
hillsides, because it lived on a mountain and could not climb at all. 

So perhaps it was also gained first in incipiently volant lineages that had
short, round wings with weak rectrices (as Archie had).

The basic technique is actually quite common in highly volant theropods too.
Owls, harriers, kiskadees, corvids and so on use it to pounce upon prey from
a lookout position (which need not be more than a meter above ground) with
minimal energy expenditure and minimal warning.

Lilienthal's hang glider experiments are really something to be considered
as an analogy. Check out this photo:

He had a launch-hill built that was elevated above the surrounding landscape
by about two times the glider's wingspan. For Archie, that would have been
between half a meter and a meter. Lilienthal's glidepath was up to 40 times
the glider's wingspan. That cannot be compared to Archie of course except in
very loose terms, but it would still mean that Archie could, from a rock or
trunk or coralhead or *anything* it could hop/scramble using hands and
feet/WAIR up (no real vertical "climbing" necessary!), achieve a glidepath
that covered a dozen meters or so[*], possibly in less time than it could
run that distance, and certainly with far less noise and energy expenditure.

To a contemporary observer, that would have made Archie the pinnacle of
efficiency. To its prey, it would have been a most dangerous predator. To
its predators, it would have been a most frustrating prey.

But perhaps Percy Pilcher is a better analogy than Lilienthal, as Pilcher
tried to evolve his gliders for powered flight but couldn't do it - the
weight added cancelled out the lift gained. Major structural changes would
have been necessary. Just the same as it was with Archie vs. later
self-powered birds. (John J. Montgomery, probably most familiar to US
listmembers, was not very keen on using ground-based launch)

It is also important that any significant Archie predators were terrestrial.
Small mammals do not use elevated lookouts today as much as they could,
because of the aerial threat. But even so, except for the smallest, they do
so - marmots, prairie dogs, black-footed cats, meerkats and so on. Even with
no flight capability at all, the advantage gained by using even the
slightest elevation to get a better view of your surroundings is immense. 

It is a better null hypothesis to assume Archie did use elevated lookouts
too, than to assume it didn't, given how widespread and phylogenetically
noninformative such behavior is among animals of comparable size even today,
under more adverse circumstances. And as soon as it did get up somewhere, it
would have been in the perfect position to maximize the usefulness of its
marginal flight capability.[**]

In essence, that would make Archie (and anything with a similar anatomy) a
ground-effect glider.



* I can find no published reference for estimates of Archie's glide ratio. A
good study would now be more important than ever, and I think a rather
accurate estimate can be made, given the quality of the fossil record. But
it is really important to consider ground effect, because there would not
have been an easy way for Archie to get out of it - with no significant
vertical-climbing ability nor powered-flight capability, it would have by
default been largely limited to the ground-effect zone, where the glide
ratio is (IIRC) better. (Lilienthal, Pilcher and Montgomery all found it
problematic to get out of ground effect, and it may be significant that
Pilcher suffered fatal structural failure and Lilienthal fatally stalled
just above the ground effect zone)

** That such an approach is very useful even to perfectly volant theropods
can be seen when approaching birds resting on a slightly elevated position,
e.g. seagulls on breakwaters. If yo do not run at them but approach at a
slow but steady pace, they will usually choose to glide some distance away,
rather than flying up and leaving the area for good. There is little point
in expending energy for powered flight as long as simply putting some
distance between you and the disturbance by a far more energy-efficient way
will do.